The chairman of a closure- threatened Scottish charity which refuses to allow gay couples to adopt has condemned the raising of children by same sex couples as a "terrible social experiment".

Father Tom White of Glasgow-based St Margaret's Children and Family Care Society, said the country was "on the brink of declaring illegal" the belief that every child, where possible, deserves a mother and father.

The service has announced it is prepared to go to the Court of Session in Edinburgh to fight to keep its status. It hopes to overturn a recent ruling by the Office of the Scottish Charity Regulator (OSCR) that its policy discriminates against same-sex parents.

In the society's annual report, Father White wrote: "Society at large is embarking on a terrible social experiment with children, treating them as commodities that people have a right to, such as gas, electricity, or a hotel room.

"Our country is on the brink of declaring illegal the belief that every child where possible deserves a mother and father."

Copies were handed yesterday to supporters and adoptive parents at its yearly thanksgiving mass at St Andrew's Cathedral in Glasgow.

Fr White called on those who supported St Margaret's to take on the legal fight.

The OSCR found the charity was operating in breach of the Equality Act 2010. The criteria it applied to people who inquire about assessment as prospective adoptive parents "discriminated unlawfully" against same-sex couples.

The society, which matches potential carers with children in need, prioritises couples who have been married at least two years. OSCR had earlier ruled that the policy was discriminatory and flouted equality laws. The charity is seeking to have the ruling overturned at the Scottish Charities Appeal Tribunal, but is prepared to take it to the Court of Session.

Fr White described the projected legal costs as frightening.

He referred to an "aggressive" campaign by the Secular Society to have the charity disassociate itself from its Catholic ethos or face the removal of its charitable status, which would effectively bring about its closure.

Fr White called on those who supported St Margaret's through annual crib donations and prayers to take on this [legal] fight.

He told worshippers: "What we have to look at are the implications. If the charity is removed from the Scottish Charity Register, is it viable as an organisation?"

He said about £100,000 of funding came from the Catholic Church, adding: "So if we were to become disassociated, there would be implications about how viable St Margaret's would be as a service in the longer term."

The society announced plans to move to better accommodation to open a new family centre.

Board member Brian McGuigan said the threat to St Margaret's had galvanised the wider Catholic community, and said the charity's origins and identity were 'inseparable' from the church.

Archbishop of Glasgow, Philip Tartaglia said: "The whole church is united in support for its work and we hope that common sense will prevail, and it will be allowed to continue to serve children in Scotland who need loving families."

Glasgow City Council has launched a major advertising campaign with one billboard poster placed prominently on the M8 south of the Kingston Bridge showing two men and a baby in its drive to encourage gay adoption.

A council spokesman said: "Fr Tom White is entitled to his views. They are not shared by all sections of civil society and that includes Glasgow City Council."